Synthetic thickening polymers in the form of inverse latices are described as being able to be used in the manufacture of topical compositions, in the European patent applications published under the numbers EP 0 716 594, EP 1 047 716, EP 1 056 805 and EP 0 503 853.
However, most of these thickeners are incapable of thickening oil phases.
The European patent application published under the number EP 0 406 042 discloses cosmetic compositions in the form of water-in-oil emulsions containing as thickener a polymer with a low proportion of units containing ionic groups, for instance the copolymer of N-dodecylacrylamide and of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) in a 96.5/3.5 weight proportion or the copolymer of N-tert-butylacrylamide and of 2-acrylamido-2-methylpropanesulfonic acid in a 97.9/2.1 weight proportion. Such copolymers are difficult to use in the cosmetic industry since they must be neutralized before use, and since their dissolution in oils often requires the use of a cosolvent. Furthermore, their oil-thickening capacity is low.
It is for this reason that the only compounds known to date having this property are the copolymers sold under the name Intelimer, which are hydrophobic copolymers bearing long pendent alkyl chains, which crystallize under cold conditions to form clusters that bring about thickening of the medium. Such polymers of the type such as copolymers of an alkyl acrylate and of (meth)acrylic acid are described in the American patents published under the numbers U.S. Pat. No. 7,101,928 B1 and U.S. Pat. No. 5,736,125. However, the use of these products is not simple since the polymer needs to be dissolved in the oil under hot conditions, followed by cooling to bring about crystallization of the chains. Furthermore, they are by nature heat-sensitive and compositions thickened with a polymer of this type are difficult to market in hot countries.
This is why the Applicant has sought to develop novel polymers that are capable of thickening organic and oil phases, which do not have the drawbacks mentioned above.